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T

Trimglafix

Hi, I'm looking for some advice.
Basic question is:
Will any harm be done if my leisure battery positive and vehicle battery positive become connected to one another?

Explanation:
I want to set up my camper van so that I can switch on the cameras from either the drivers seat or when in the back. It is easier to wire if I can have a switch taking power from the vehicle battery when in the drivers seat and a switch taking power from the leisure battery when in the back.
if both switches are unintentionally turned on this would lead to the two positives having a direct route to each other. I am concerned this could lead to the lower charged battery taking the charge from the other battery (or blowing the fuse if over its rating).
If this is a problem would a simple diode placed near the switch stop the problem?

Thanks in anticipation.
Anton.
 
If you switched them both on together you would be putting the batteries in parallel with each other. A relay could help you here, you could power it from either but keep the batteries electrically separated.
 
A diode in each wire from battery to switch would work, the size of the diodes depends on power requirement of cameras.
The supply to the cameras would be reduced by 0.7 volt by the diodes but that should be OK.
 
Thank you all for your replies; each one was helpful.
As I do have to keep the batteries electrically separated and each requires extra parts / wiring I think I will keep it simple (in technical terms only!) and run the wires required to operate the cameras off the leisure battery from both locations.
I was surprised at the voltage drop a diode causes, hence my reason for not pursuing that option (although you are correct in assuming the cameras will still be well within their recommended voltage tolerances).
I have used diodes elsewhere and now realise I need to learn a bit more about them to check the exact effect they have on a circuit.

Regards
Anton
 
all silicon diodes drop 0.6V - 0.7V. germanium diodes are less. about 0.2V.
 
If you use diodes, likely they will be silicon, with approx. 0.7V drop as mentioned. You don't say what current the camera(s) draw, if low current e.g. total well under 1A, then a basic leaded diode (1N4007 etc.) will suffice, but if close to 1A or higher, you need to start thinking about the rating of the diodes, and they may need a heatsink.

If you opt for a cable that could connect the two batteries, if one battery is quite discharged and the other is fully charged, the current flowing between the two batteries if accidentally connected together could be quite high. Low current equipment wire or thin cable (e.g. 0.5mm2 cross section) could easily get warm, hot or even melt.

Unless there is some reason why you need to power the camera(s) from either battery, I'd probably opt for wiring that only connects to one battery.
 
Last edited:
I would not recommend connecting the two batteries together for the reasons suggested,plus it may confuse other parts of the system.If you have the interconnection facility for two diodes,then put a relay in instead. You could use the NC contacts for the favoured battery or have it switched to either from 0. You can get some snazzy bank switch isolators used on watercraft,and do it manually. Hidden diodes in this application may fail and not give any indication they have done so till much later.
 
Once again thank you for all replies & apologies for my delay in posting back here. I found each one very useful & informative.

I have taken a single positive wire from the leisure battery & run it up to the cab area. I have then used a positive from the ignition switch (Acc position) to activate a relay. The leisure battery wire then goes through a manual switch to turn on the camera. The negative is the van body in all cases.
The set up in the back is simply a switch on the leisure battery wire.
I haven't put any diodes in therefore both monitors come on when either is switched on, but that is not a problem.

This seems to satisfy all my requirements & keeps the two batteries separate (I'm glad I asked & more pleased that I received knowledgeable replies!).
Thanks.
 

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